Variable-capacity metering pump



Oct. 29, 1957 D. B. HORTON El' AL VARIABLE-CAPACITY METERING PUMPOriginal Filed May 17, 1954 4 Sheets-Sheet 1 I A\' V ENTORS 00A/EL 50Na. Hon ra/v i Vvousl. A s ./oH/vs roN mm @H4614 Mw ATTORNEYS Oct. 29,1957 D. B. HORTON ETAL 2,811,108

VARIABLE-CAPACITY METERING PUMP Original Filed May 17, 1954 4Sheets-Sheet 2 ///IIIIIIl/IIII/ lf/ ////x /////Vwm k f ATTQRNHS BY/ZOct. 29, 1957 D. B. HoRToN Erm. 2,811,108

VARIABLE-CAPACITY METERING PUMP 4 Sheets-Sheet 3 Original Filed May 17.1954 Oct. 29, 1957 D. B. HoRToN ErAL 2,811,108

VARIABLE-CAPACITY METERING PUMP Original Filed May 17. 1954 4Sheets-Sheet 4 ummmml "Wg-l INVENTORS www M7 www Y 2,811,108VARIABLE-CAPACITY MErEnlNG PUMP Donelson B. Horton and Douglas Johnston,Huntsville, Ala., assignors to John Blue Company, Incorporated,Huntsville, Ala., a corporation of Alabama This invention relates tovariable-capacity metering pumps, and more particularly to pumps formetering a pressurized normally-gaseous liquid. This invention is animprovement on the metering pump disclosed and claimed in the copendingapplication of John Blue, Serial No. 80,957, tiled March l1, V1949, nowPatent No. 2,696,785. This application is a division of ourapplication'Serial No. 430,087 liled May 17, 1954, now Patent No.-2,771,846,` granted November 27, 1956,

Thel pump disclosed in the aforementioned applications isusedprincipally tonaccurately meter anhydrous ammonia for application tothe. soil for agricultural purposes. While very satisfactory for itsintended `purpose in actual practice, the pump is Asubject to severalimprovements which bothincrease its metering accuracy andrreducemaintenance expense. The pump disclosed in the above applications is ofthe positive displacement type, having a piston or pump plunger providedwith an inlet check valve and reciprocable in a pumping cylinder. Thecylinder is provided with an outlet check valve that is loaded by thepressure of the source of supply of the liquid being pumpedindependently ofthe Y rod is intermittently engaged and pushed inwardlyof the pumping chamber for a discharge or pumping stroke by either areciprocating crosshead driven by a connectingrod and crankshaftarrangement, or a rotating cam. The suction stroke of theV piston rod,i. e., movement of the rod outwardly of the pumping chamber, is effectedby springs and also by the pressure of the source of supply of theliquid being pumped. The pump is of variable capacity, and the capacityis adjustable by means which serve to limit the stroke of the pistonrod.

Y Inthe aforedescribed pump, when its capacity is adjusted to a settingbelow maximum, there is lost-motion engagement between the reciprocatingcrorsshead or rotatingcam and the piston rod. It also will be seen that,as the setting of the pump is progressively adjusted toward minimum, theextent of lost motion in the aforementioned engagement increasescorrespondingly. Fur- Vtherit will be seen that, since the suctionstroke of the pump is effected solely by the aforementioned springsandthe pressure of the source of supply of the fluid being pumped, thesuction stroke is not accomplished VLby a positive drive. In the eventthat the packing gland for Vthe piston or pump rod is too tight, thepiston rod mayltend to stick so that a full suction stroke, at theadjusted setting of the pump, is not obtained, with consequent meteringinaccuracies. The same result can possiblybe obtain at higher rates ofpump operation, in that a full suction stroke may not occur before thepiston rod States Patent-O M is again engaged by the positive drive forits discharge stroke. Furthermore, because the suction stroke of thepump is notobtained by a positive drive, the drive for the pump is underan intermittent or pulsating load.

' Additionally, the pump shown in the aforementioned applications has avalve-controlled purging passageway Il" on line'6-6 of Figure l.

2,811,108 Patented oct. 29, 1957 extending lbetween the pumping rchamberand the outlet chamber at the discharge side ofthe outlet check valve.The valve controlling the passagewayV must, of course, be constructed towithstand the full pressure developed within the pumping chamber.

`In addition to the foregoing, the pump shown in the aforedescribedapplications has aV partially-open crankcase so that` ay portion, of thepiston or pump rod, and the mechanism for adjusting its stroke, 4areexposed. Since the pump is utilized by farmers, there is a stronglikelihood of dirt or trash accumulating in the aforedescribed exposedportion in the c'rankcase with resultant undue wear and abrasion of thethus-exposed moving parts of the pump. Y

l Therefore, it is an object of this invention toprovideavariable-capacity metering pump of the reciprocating type whereinpulsations in the loadon the pump drive aresmoothed out as much aspossibley and the evenness of the load on the pumpdrive lis at maximum.

-It is .another object of this invention to provide'a pump of the typedescribed that is accurate at higher rates of operation. e

It isanother object of this invention to provide means for` purging thepumping chamber of the type described which eliminates the need forahigh-pressure valve.

vIt is another objectV of this invention to' providea pump ofthe typedescribed that has a housing completely enclosing all moving parts ofthe mechanism for adjusting theV capacity of the pump.

`Other objects, andadvantages' ofthe invention "will become apparentfrom the following description `and accompanying drawings, in which:

VFigurelisaa' side elevationalview'of a metering Figure 5 is an enlargedfragmentary top plan viewlof the pumpl shown in Figure 2, with partsbroken away to illustrate details.

Figure 6 is an enlarged vertical sectional view taken Figure 7 is anenlarged, vertical, sectional view taken on line 7-7 of Figure 3.

AFigure 8 is an enlarged, fragmentary, sectional `view taken on line 8-8of Figure 2. t

Figure 9 is an enlarged fragmentary sectional view taken on line 9 9 ofFigure 1. s

Referring now to the drawings, there is shown a pump embodying thisinvention. The pump includes an openended cylinder 10 having exteriorcircumferential end tlan'ges 12 and 14 and a liner 16 fitting against aninterior shoulder 18. Engaging against the other endof the liner 16',with a gasket 20 therebetween, is a plug-like member 22 having a centralvalve po'rt 24`therethrough provided with an annular valve seat 26 atits -outer endtr A flanged cylinder head 28, secured by cap screws 30 tothe cylinderl flange 14, has an annular boss 32.tting into one end 0f`the' cylinder 10 and engaging against thegplug-like member 22, with anapprop-riate gasket 34 therebetween to retain the member 22 and theliner 16in proper Vposition within the cylinder. The boss 32 is providedwitha central circular recess 36 opposed to the valve'seat'26 to form adischarge chamber 38 from which a passageway 40 leads to raninteriorly-threaded'opening 42 (FigureS) in the cylinder head 30 forconnection to a discharge con` collar 162 are engaged so that on thereturn stroke lof theA crossheadA 148 the length of the suction strokevof the piston 84 will be at a maximum.

Referring now to Figure 4,.it will be seen that in this showing theadjusting nut 166 has been threaded rearwardly on the piston rod 86, sothat in its return stroke the crosshead 148 will not pull the piston rod86 rearwardly as far as when the nut 166 is in the position shown inFigure 3. Accordingly, as the crosshead 148v starts its dischargestroke, it moves a .considerable distance before engaging the end of thepiston rod 86 to effect the discharge stroke of the same. Consequently,a lostmotion connection exists between the piston 'rod' 86 and thecrosshead 148 at any position of adjustment of the nut 166 betweenminimum and maximum capacity of the pump. Y

As described before, the inlet chamber 100 and the pumping chamber 98 ofthe pump are under considerable pressure even during the suction strokeof the piston 84. This pressure, of course, urges the piston rod 86outwardly of the pump chamber 98. Thus, while once the crosshead 148engages the piston rod 86 the crosshead and the crankshaft 150 and itsdrive are under considerable load during the pumping stroke of thecrosshead, unless otherwise provided for, the crosshead and its driveare under no load on the suction stroke. Therefore, unless otherwiseprovided for, the drive for the pump would be under a pulsating load,which would result in considerable wear and tear and possible breakageof some of the parts of the pump drive.

In order to eliminate this diiculty, a two-part transverse crossbeam 174has its upper and lower parts clamped onto a reduced portion of thepiston rod 86 and engaging against a rearwardly-facing shoulder 176thereon. Clamped between the two parts of the crossbeam 174, at each endthereof, is a necked portion of a rod 178 which extends parallel to theaxis of the piston rod 86 through aligned apertures in the crankcasehousing 70 and in the stuing box plate 74 and outwardly along thecylinder 10. On the outer end of the rod 178 is a spring-retainer washer180, retained by a snap ring 182, and between the washer 180 and thebottom 184 of a counterbore extending through the stuffing box plate 74and into the housing 70 is a coil compression spring 186. Preferably,each spring 186 is enclosed in a separate tube 188 having one endthereof threaded into the flange 12 (Figure 5) on the end of thecylinder 10 and the other end thereof closed by a threaded plug 190. Theintermediate portion of each tube 188 is supported in an apertured ear192 on the flange 14 on the other end of the cylinder 10.

From the aforedescribed construction, it will be seen that the springs186 oppose the suction stroke of the piston rod 86 so that the drive forthe pump will be under a load during the suction stroke of the latter.At the same time, the springs 186 store up energy to somewhat relievethe load on the pump drive during the discharge or pumping stroke of thepump. Thus, when the pump is adjusted for less than maximum capacity andthe crosshead 148 starts its discharge stroke, the springs 186 tend toymaintain the flange 164 on the adjusting nut 166 in engagement with theend of the collar 162 for an appreciable extent of the discharge strokeof the crosshead 148 and until the pressure in the pump chamber 98 isbuilt up to such an extent that the springs 186 cannot overcome thesame. At this time, the bottom 160 of the recess 156 in the crosshead148 catches up with and engages the end of the piston rod 86 to effect apositive pumping stroke of the latter. Therefore, it will be seen thatjars and impacts occasioned by the lost-motion connection between thepiston rod 86 and the crosshead 148 are substantially lessened andminimized by the action of the springs 186.

Referring now to Figures 1 to 6 of the drawings, it will be seen thatthe crankshaft housing 70 includes two chambers 194 and 196joined by alower passageway 198 beneath the crosshead bearing 149,;thjchamber 194serving as an actual crankcase and the chamber 196 serving as a housingfor the pump-capacity-adjusting mechanism and for the exposed portionofthe piston' rod 86 and exposedl ends of the spring rods 178. Inoperation, the crankcase chamber 194 normally has oil therein which canflow, via the passageway 198, into the chamber 196 to maintain themoving parts therein rin a lubricated'condition. The top of the chamber196 is' opem save for la 'longitudinally-extending bridge member 200,and. the upper edges ofthe end walls of ther chamber 196 are inclinedlaterally and downwardly to provide two upper openings 202 and 204(Figure 6) to the chamber, one on each side of the bridge member 200,the upper edge f each opening lying in a downwardly and'laterally-inclined plane. Closing the opening 202 is a closureplate206, secured to the housing 70, as by screws 208. An apertured ear 210at the lower edge of theclosure plate 206 has a wing bolt 212 extendingtherethroughy and into a tapped opening in the crankcase housing70.V Theopening 204 on the other side of the bridge member 200 is closed by asimilar closure plate 212 having a transparent window 214 therein forviewing the scale 172. The closure plate 212 is similarly secured inposition by a wing bolt 216, but has no other securing screws. At theirupper and adjacent edges, both closure plates 206 and 212 are providedwith transversely-overlapping apertured ears 218 and are pivotallyconnected together by a longitudinally-extending pivot pin 220, so thateither closure plate may be unfastened from Vthe crankcase housing 70and raised upwardly for inspection of the interior of the chamber 196and the parts therein.

Considering again the mechanism for adjusting the capacity of the pump,it will be seen that at each discharge stroke the piston 84 is pushedinwardly of the pumping chamber 98 almost into engagement with themember 22, so that at each discharge stroke of the pump the volume ofthe pumping chamber 98 is reduced to a minimum. Because of this fact,even if some gas is formed or enters into the cylinder, the effect ofsuch gas on the accuracy of metering of the pump is minimized. On theother hand7 if the volume of the pumping chamber is not reduced to aminimum at each discharge stroke of the pump and gas is formed or entersinto the pumping chamber, such gas might tend to accumulate until thepump became gas-locked.

It thus will be seen that the objects of the invention have been fullyand effectively accomplished. It will be realized, however, that variouschanges may be made in the specific embodiment shown and described forthe purpose of illustrating the principles of the invention. Therefore,this invention includes all modifications encompassed within the spiritand scope of the following claims.

We Claim:

l. A variable-capacity pump for accurately metering a pressurized uidcomprising: means defining an expansible pumping chamber having amovable wall; a reciprocable pump rod secured to said wall and extendingoutside said chamber for moving said wall inwardly and outwardlythereof; a fixed throw reciprocating driving member opposed to the outerend of said rod and engageable with said rod end to effect a dischargestroke thereof; means defining a sleeve extending from said member andenclosing the end portion of said rod; means defining aradially-inwardly-extending circumferential ange on said sleeve; meansdefining a radially-outwardlyextending circumferential flange on saidrod within said sleeve engageable with saidsleeve iiange to eifect asuction stroke of said rod, said rod flange means being threadedlymounted on said rod for axial adjustment therealong to vary the capacityof the pump; and a. longitudinally-extending scale on said rod,cooperable ,with-referencefrneansassociated with said4 rod flang meansfor indicating the adjusted capacity of the pump. '2. In avvariable.capacity pump the combination comprising: means defining an expansiblepumping chamber having amovable wall; a reciprocating pump rod securedto said wall and extending outside said chamber for moving said wallinwardly and outwardly thereof for `discharge andVV suction strokes,respectively; a fixed-throw vreciprocating driving member having anabutment surface engageable with the outer end of said rod for movingthe latter inwardly of said chamber; a sleeve on said driving memberenclosing said rod outer end and having a radially-inwardly extendingflange; and a nut threaded on saidrod and having a radially outwardlyextending flange interposed between said surface and said sleeve flangeand engageable by the latter Yfor moving said rod `outwardly of saidchamber, rotation of said nut on said rod with resulting axial movementtherealong serving to adjust the capacity of the pump, said nut beingelongated and having a portionV disposed outside said sleeve tofacilitate access to said nut.

t 3. The structure dened in claim 2 including a housing completelyenclosing the driving member, the sleeve, the nut, and that portion of`the rod extending outside the chamber, said housing having an openingtherein for access to the nut, and including a removable closure forsaid opening.

References Cited in the file of this patent

